EP0454595A1 - Process and apparatus for treating waste by means of vermicomposting - Google Patents

Abstract

Process for treatment of organic waste by vermicomposting in at least one vermicomposting unit (2), according to which in the said unit there is established a vertical stack (21) of a substrate consisting of at least one upper layer (22) of organic waste introduced through the top, of at least one lower layer (23) of organic residues which are removed through the bottom, and of a population of earthworms dispersed in the stack (21) and travelling upwards, the outer surface of the stack forming essentially the only interface for exchange of the substrate with the exterior. The vermicomposting unit (2) is arranged in an enclosure (1) insulating it from the surrounding air, and a controlled atmosphere (24) is established in the enclosure directly in contact with the side surface of the stack (21). <IMAGE>

Description

The present invention relates to the treatment of organic, domestic, industrial, agricultural, etc. waste, by vermicomposting, with a view to obtaining organic residues, such as potting soil or humus, having a utility or value, for example for amending a ground.

Vermicomposting means any aerobic fermentation of organic matter, in the presence of earthworms, more colloquially earthworms, contributing to spraying, aeration, and a mixture of the substrate during fermentation.

In accordance with French patent application No. 89 14616 filed in the name of the Applicant, a vermicomposting treatment process has been described, according to which, in a unit consisting of a container with a perforated side wall of the mesh type, a pile is established or vertical load of a fermentation and transformation substrate, composed of one or more upper layers of organic waste introduced sequentially from the top of the tank, and one or more lower layers of organic waste sequentially discharged from the bottom of the same tank ; and a population of earthworms is dispersed in the heap, progressing upwards, each new evacuation and each new introduction into the tank being made according to the progression of the worms upwards. According to this method, apart from the downward movement of the different layers of substrate, the latter remains in mass and is not agitated by any external mechanical means, and no liquid or gaseous current is injected into this mass. This means that essentially the external surface, and in particular the lateral surface of the pile, constitute the only interface for exchange of the substrate with the outside.

Traditionally, vermicomposting is carried out in open landfills, and depends for its effectiveness on ambient conditions, that is to say those of the outside atmosphere, temperature and humidity, essentially. However these conditions vary between day and night, and from one season to another, while earthworms used for vermicomposting need for their life and development of stable conditions of temperature, humidity, and oxygenation, for example between 25 and 30 ° C, between 50 and 70% humidity, and at least 15% oxygen, for the species of EISENIA ANDREI.

The purifying action of earthworms is therefore dependent on the ambient environment, and any alteration of the latter, on the one hand leads to a low transformation yield, and on the other hand leads to the development of undesirable side reactions, for example anaerobic fermentation leading smelly gases; and there may be the appearance and development of pathogens in the substrate or compost.

Starting from the process described by French patent application No. 89 14616, the present invention relates to operating conditions making it possible to optimize the living and development conditions of earthworms.

According to the present invention, there is a vermicomposting unit, or a battery or plurality of said units in a single enclosure separating it, or separating them from the ambient air, and a controlled atmosphere is established in the enclosure, directly at the contact with the lateral surface of the heap, or heaps in fermentation and transformation in the different units.

Preferably, the controlled atmosphere consists of a controlled air flow, circulating from an inlet to an outlet of the enclosure, in contact with the pile or piles of substrate. And, at least one of the following control parameters, namely oxygen content, carbon dioxide content, and temperature, is regulated and the air flow circulating in the enclosure is regulated to maintain the parameter (s) of control at a value or in a preset area.

The existence of a controlled atmosphere in contact with the heaps of substrate makes it possible to control the fermentation or composting process from the outside, the oxygen or water content for example of the controlled atmosphere determining the rates of transfer of these elements to the substrate, and therefore the earthworms.

The present invention also includes the following embodiments.

The air flow introduced into the enclosure is taken from a pit for receiving organic waste for vermicomposter. This makes it possible to avoid the release of malodorous gases into the atmosphere, by deodorizing them during their passage inside the enclosure, where they are oxidized by chemical and / or biochemical means.

In addition, the control parameters are regulated, depending on the climatic conditions outside the enclosure. This allows in particular to take into account the thermal nycthemeral cycles, to allow for example a renewal of the air introduced into the enclosure, at the coolest or warmest periods, according to the climatic conditions.

In any case, the invention will be well understood with the aid of the single figure representing the entire installation for implementing the method.

As illustrated in the drawing, this installation comprises an enclosure 1 inside which there are four vermicomposting units 2. Each vermicomposting unit 2 comprises a tank 25 whose side wall, for example mesh, is permeable to gases and liquids ; in each tray is disposed a load 21, vertical pile or heap of a substrate, composed of upper layers 22 of organic waste introduced from above, and lower layers 23 of organic residues discharged from below. Each vermicomposting unit 2 contains both the organic matter to compost, but also the population of earthworms responsible for transforming it, and gradually moving upwards. These are earthworms which belong, for example, to the species of EISENIA ANDREI, and which live and develop in conditions of temperatures between 25 and 28 ° C, a relative humidity of 50 to 70%, and a rate of oxygenation of the air by at least 15%.

The introduction of organic waste to be composted, which has been previously moistened with water under the nozzle 12, from the top of the vermicomposting tanks or units 2, is done in a controlled and discontinuous manner, via a traveling crane 13 comprising buckets 14.

Obviously, it is entirely conceivable to use other means of introduction, such as for example a treadmill.

The evacuation of organic vermicomposting residues is carried out at the bottom of each vermicomposting unit 2, by a chain comprising scrapers 15. These vermicomposted residues are thus evacuated outside the enclosure 1, to be conveyed by a belt conveyor, not shown, in a receiving container, before their further processing.

For the arrangement and operation of vermicomposting units, reference will be made more particularly to French patent application No. 89 14616, the content of which is incorporated into the present application, as necessary.

This enclosure 1 comprises an orifice 3 formed in the lower part of one of its side walls 4a, and an orifice 5 formed in the upper part of another of its side walls 4b. Each orifice 3.5 comprises a fan with blades 6, and it is more or less closable by a flap 7 movable around a hinge 8. These means make it possible to circulate a flow of air in the enclosure 1, establishing a controlled atmosphere in the latter.

To regulate at least one of the following parameters in enclosure 1, namely oxygen content, carbon dioxide content, temperature and humidity, of fresh air, in particular from a waste receiving pit 9 to vermicomposter, is introduced inside this enclosure 1 by the fan 6, arranged in particular above the pit 9. This fresh air, and in particular the smelly molecules which it contains, is used as a source of heat, energy and biogenic elements, after their degradation by microorganisms contained in organic matter to be composted, by earthworms.

The degradation of complex organic molecules in waste, into simple molecules, by fermentation and oxidation is exothermic. It causes an increase in the air temperature inside the enclosure. In addition, it gives off carbon dioxide and water, which leads to an increase in the relative content of these in the atmosphere inside the enclosure. This hot air, charged with carbon dioxide and water vapor, is then evacuated outside the enclosure by the fan 6 placed in the orifice 5.

This exhausted hot air can be used as an energy fluid and as a growth agent to allow accelerated development of plants in a greenhouse not shown. Indeed, the chlorophyll function which conditions plant growth is favored by air containing a high relative carbon dioxide content, for example greater than 0.3%, a high relative humidity of between 90% and 100% and a temperature higher than 30 ° C.

To control the carbon dioxide and oxygen content of the gaseous atmosphere inside the enclosure 1, as well as the relative humidity rate and the temperature thereof, sensors 10, 11 of the sensor type inductive, capacitive or other, are arranged inside this enclosure. They transmit signals representative of the selected control parameters to a calculation and programming means such as a computer or a PLC not shown. This calculation means, depending on the information received from the sensors, will trigger a more or less significant opening of at least one flap 7, or an operation of at least one fan 6, which will allow the supply of a more or less significant air flow inside the enclosure, restoring the control parameter (s) to a value or in a pre-established zone. In this way, the atmosphere in enclosure 1 can be kept at a minimum oxygenation threshold, characterized by a minimum value of the oxygen rate or a maximum value of the carbon dioxide rate. It is also possible to maintain the atmosphere at a minimum temperature threshold.

Obviously, this automaton can, thanks to the programs it contains, regulate the control parameters inside the enclosure, according to the external climatic conditions, which are supplied to it by a temperature sensor not shown. Therefore, the control parameters can be regulated, taking into account the thermal nycthemeral cycles for example, to allow air renewal at the coolest periods, depending on climatic conditions.

Likewise, the air renewal cycles can take into account the hours of unloading of waste inside the pit 9.

The control of the carbon dioxide content inside enclosure 1 also makes it possible to indicate if the crossing of a critical threshold is reached, and thus to prohibit any access to the interior of this enclosure personnel, due to the harmfulness to the body of this gas.

The humidity inside the enclosure 1 can be controlled by adjusting the spraying 12 of the waste, or the movement of the strip 13.

Finally, the circulation of the air flow can be done by simple thermosiphon.

Claims (10)

Method for the treatment by vermicomposting of organic waste in at least one vermicomposting unit (2), according to which in said unit a vertical pile (21) of a substrate is established, consisting of at least one upper layer (22) of organic waste introduced from above, at least one lower layer (23) of organic residues discharged from below, and a population of earthworms dispersed in the heap (21) and progressing upwards, the external surface of the heap constituting for essentially the only interface for exchanging the substrate with the outside, characterized in that the vermicomposting unit (2) is placed in an enclosure (1) separating it from the ambient air, and a controlled atmosphere is established (24) in the enclosure, directly in contact with the lateral surface of the pile (21). Method according to claim 1, characterized in that the controlled atmosphere (24) consists of a controlled air flow, circulating from an inlet (3) to an outlet (5) of the enclosure, in contact with the pile ( 21) of substrate . Method according to claim 2, characterized in that at least one of the following control parameters, namely oxygen content, carbon dioxide content, humidity and temperature, is regulated and the circulating air flow is regulated in the enclosure to maintain the control parameter at a value or in a preset area . Method according to claim 2, characterized in that the air flow is regulated by the flow introduced and / or the flow extracted from the enclosure . Method according to claim 2, characterized in that the air flow introduced into the enclosure is taken from a pit (9) for receiving organic waste to be obtained from the vermicomposter . Method according to claim 1, characterized in that the humidity of the pile is controlled by soaking (12) or spraying the waste before it is introduced into the pile . Method according to claim 2, characterized in that the control parameter is regulated, as a function of the climatic conditions outside the enclosure . Process according to Claim 2, characterized in that the atmosphere in the enclosure is controlled at a minimum oxygenation threshold, characterized by a minimum value of the oxygen rate or a maximum value of the carbon dioxide rate of l 'controlled atmosphere . Method according to claim 2, characterized in that the atmosphere in the enclosure is controlled at a maximum temperature threshold. Installation for implementing the method according to claim 1, comprising a vermicomposting unit (2), comprising a tank (25) whose side wall at least is permeable, means (13) for introducing organic waste from above , in the tank, and means (15) for evacuating organic residues from below, from the same tank, characterized in that a plurality of vermicomposting units (2) is arranged in the same enclosure (1) separating them ambient air, and making it possible to establish a controlled atmosphere directly in contact with the various piles (21) contained by the various tanks.

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